An Italian Space Agency satellite designed to minimize the effects of non-gravitational perturbations on its orbit for studying general relativity. The satellite launched from Kourou in February 2012 on the maiden flight of the ESA’s Vega rocket. The spherical satellite was placed in a circular orbit with an altitude of 1 450 km. The spacecraft is made of high-density tungsten alloy and covered with 92 cube corner mirrors that reflect an incoming laser beam back toward the source, allowing measurements of the satellite’s position with extremely high precision. The data analysis of the first years in orbit demonstrate that the satellite is behaving as predicted: like a ‘drag-free test particle’ in the gravitational field of the Earth.